1.5-Dimensional Circular Array Transducer for In Vivo Endoscopic Ultrasonography

Objective:
Traditional endoscopic ultrasonography (EUS), which uses one-dimensional (1-D) curvilinear or radial/circular transducers, cannot achieve dynamic elevational focusing, and the slice thickness is not sufficient. The purpose of this study was to design and fabricate a 1.5-dimensional (1.5-D) circular array transducer to achieve dynamic elevational focusing in EUS
in vivo
.
Methods
: An 84 × 5 element 1.5-D circular array transducer was successfully developed and characterized in this study. It was fabricated with PZT-5H 1-3 composite that attained a high-electromechanical coupling factor and low-acoustic impedance. The acoustic field distribution was measured with different transmission modes to validate the 1.5-D elevational beam focusing capability. The imaging performance of the 84 × 5 element 1.5-D circular array transducer was evaluated by two wire phantoms, an agar-based cyst phantom, an
ex vivo
swine pancreas, and an
in vivo
rhesus macaque rectum based on multifocal ray-line imaging method with five-row elevational beam steering.
Results
: It was demonstrated that the transducer exhibited a central frequency of 6.47 MHz with an average bandwidth of 50%, a two-way insertion loss of 23 dB, and crosstalk of <−26 dB around the center frequency.
Conclusion
: Dynamic elevational focusing and the enhancement of the slice thickness in EUS were obtained with a 1.5-D circular array transducer.
Significance
: This study promotes the development of multirow and two-dimensional array EUS probes for a more precise clinical diagnosis and treatment.